Conceptual system design of non-nuclear grade IS process to be coupled with the HTTR

Transcription

1 Conceptual system design of non-nuclear grade IS process to be coupled with the HTTR N. Sakaba, H. Sato, H. Ohashi, T. Nishihara, K. Kunitomi Monday, 16 April 2007 IAEA-CN-152, Oarai, Japan Japan Atomic Energy Agency

2 Outline of my presentation Summary of JAEA s HTTR project Establishment of Non-Nuclear Grade IS Process Objective Why non-nuclear? Why HTTR-IS? R&D for non-nuclear Individual research item and its results Conclusion International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 2

3 Summary of the HTTR project Objective Establishment of HTGR technology Accumulation of long-term operation data Demonstration of inherent safety feature Establishment of heat utilization technology Demonstration of hydrogen production Reactor pressure vessel Thermal power Fuel Coolant Hot-gas-duct Inlet / Outlet temperature Pressure Major Major specification 30MW Coated fuel particle Prismatic block type Helium gas 395 o C / 950 o C (maximum) 4 MPa IS process Reactor containment vessel Intermediate Heat Exchanger (IHX) HTTR History Non-nuclear History grade chemical plant 1968 R&D on HTGR started 1990 Construction started 1998 First criticality 2001 Attained 30MW, 850 o C 2004 Attained 30MW, 950 o C (World first) 2010s To be connected to the IS process International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 3

4 Why Non-Nuclear? Why HTTR-IS? Any chemical plant, e.g. hydrogen production system, should be built as non-nuclear grade from economical point of view. e.g. Construction, Easy operation, Easy maintenance To establish the non-nuclear, several technical issues exist from safety point of view. HTTR-IS demonstration can solve technical issues HTTR-IS demonstration will acquire Public Acceptance on nuclear produced hydrogen. And then, the door will open for non-nuclear industries e.g. gas and oil companies, to enter as a construction company. International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 4

5 What technical issue? What major R&D? No-influence to the nuclear reactor during accidents and abnormal events which may occur in the hydrogen plant system. Safety philosophy should be established. a. Hydrogen explosion, toxic gas leakage b. Thermal disturbance c. Isolation nuclear system from hydrogen plant system Major R&D to be conducted: a. Establishment of evaluation methodology b. Establishment & validation of system for thermal disturbance c. Development of high-temperature isolation valve, IHX and establishment of tritium reduction methodology International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 5

6 Evaluation of Hydrogen Explosion Reactor should keep its safety against the damage from hydrogen explosion. Evaluation methodology should be established prior to safety case review by the government. Conservatively assumed sequence Pipe rupture and hydrogen leakage Mixture with air Formation of hydrogen cloud Blast Overpressure (kpa) Reactor building 10 0 Blast Distance of reduction of blast overpressure Combustible gas Cloud Dispersion 60 Distance of dispersion Concentration 4 (Vol %) Wind Leak point Pipe Dispersion towards reactor forced by wind Blast (4-75vol%) Distance of dispersion* R= 90 (M d) 0.2 ζ h ζ ws M: Volume of hydrogen, d: Diameter of rupture pipe ζ h : Ratio by leakage height, ζ ws : Ratio by wind speed Wall arrangement can reduce the distance of dispersion. * T. Murakami, et al., J. Atom. Energ. Soc. Jpn., 5, 4, 316 (2006). Evaluation methodology for hydrogen explosion was developed. International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 6

7 Absorption for thermal disturbance Absorption system which can mitigate thermal disturbance initiated by hydrogen plant is necessary for the continuous operation of the nuclear reactor. Absorption system: By-pass system Steam generator (Using evaporated latent heat of water) 10MWth Containment Vessel (Inside)(Outside) Intermediate Heat Exchanger (IHX) Steam Generator IS process 3~10MWth 7MWth Air Cooler Mock-Up Test Facility of Steam Generator with Air Cooler had built and the absorption system was successfully confirmed. International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 7

8 I. Remove HT by HPSs HPS: Helium purification system Reactor HT HPS 950 C Primary Helium 395 C III. Oxidized layer control to reduce permeability Prevention of tritium permeation H2 IHX HT II. H2 injection to decrease HT diffusion rate from primary to secondary (HTTR test item) APHX H 2 SO 4 decomposer HPS 905 C Secondary Helium 160 C 0.5O2 + H 2 O + SO2 H 2 SO 4 H2 + I2 2HI HI decomposer IV. Water injection H2O + HT HTO + H2 Remove HTO by HPS: (HTTR test item) Tritium concentration in the non-nuclear system should be lower than its limit. (HTTR data indicates that prevention of tritium permeation is necessary.) International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 8 H2 HT HT

9 High-Temperature Isolation Valve (HTIV) Major Specifications Fluid : Helium Temp.: 905 o C Pressure : 4.0 MPa Flow rate : 9,070 kg/h O.D. : mm I.D. : 204 mm Height : 3m Leakage rate Less than 4.4 cm 3 /s Drive unit Gland seal Thermal insulator Rod He gas Disk Development duration 3 years Body T. Nishihara, et al., J. Atom. Energ. Soc. Jpn., 3, 4, 69 (2004). He gas ½ scale model of high-temperature isolation valve ½ scale model of High-Temperature Isolation Valve was developed and confirmed its sufficient seal performance up to 905 o C. International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 9 Seat

10 Water & H2 injection to secondary cooling system for reducing tritium concentration. (To be confirmed at HTTR operation) Conclusion Appropriate distance between reactor and hydrogen plant. (Evaluation completed) High-temperature Isolation Valve. (½ size developed) Intermediate Heat Exchanger. (Equipped in the HTTR) HTTR Nuclear grade IS process Non-Nuclear grade Steam Generator for thermal disturbance. (Mockup test completed) Technical feasibility was examined and the conceptual system design was completed on non-nuclear grade HTTR-IS hydrogen production system. Basic design and safety analysis are in progress. International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 10

11 Welcome to JAEA for participating in the HTTR project to globally commercialize the VHTR hydrogen production systems. Thanks for your attention. International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 11

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13 HTTR current R&D status HTTR Graphite-moderated/helium gas-cooled HTGR Control room Intermediate heat exchanger (IHX) Containment vessel Reactor pressure vessel Near term test plan FY2007: Long-term rated (850 C) operation (30 days) Loss of forced cooling test at low power level FY2008: Long-term high-temperature (950 C) test operation (50 days) Loss of forced cooling test at high power level Vessel cooling system stop test (1 out of 2) FY2009: Loss of forced cooling test at full power Vessel cooling system stop test (2 out of 2) : All blackout test International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 13

14 Proposed R&D towards Non-Nuclear Non-nuclear grade H2 production system Establishment of safety philosophy Event selection Probabilistic safety assessment Establishment of safety criteria Exemption from internal events H2 plant thermal load disturbance absorption External events Countermeasure for H2 explosion Countermeasure for toxic gas inflow to reactor control room Exemption from radioactivity release control Reduction of tritium releasing to environment & mixing to product H2 Development of hardware for separation of nuclear from H2 plant Isolation of H2 production system Control of thermal load of H2 production system Development of High- Temperature Isolation Valve (HTIV) International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 14

15 Safety criteria to be established Event Flammable gas release Safety Criterion Gas concentration of intake air from ventilation system is lower than its explosion limit. Overpressure on the reactor building is lower than 20kPa. (In case of wall thickness of 30cm) Function Preventing an explosion in the reactor building. Preventing the top-level safety-related systems inside the reactor building. Toxic gas release Gas concentration in the control room is lower than its limits for long-lasting adverse health effects. Safeguarding reactor operators against hazard. International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 15

16 Dynamic simulation code development IHX High-temp. isolation valve Helium cooler Auxiliary cooling system Reactor IS process Steam generator Helium gas circulator 2 nd He system Primary system Primary pressurised water cooler Dynamic simulation code base on RELAP5 Mod 3 is under developing and the code can: Evaluate the credibility of the cooling system and plant dynamics of the HTTR-IS system during abnormal events initiated by the IS process Be utilized for the safety case review by the government Component model Reactor 1) Steam generator 2) Heat exchangers IS process ( in progress) Reactor kinetics Thermal hydraulics Chemical reaction 1) K. Takamatsu, et al., Trans. At. Energy Soc. Japan., 3[1], 76 (2004). 2) H. Ohashi, et al., Nucl. Eng. Des., 236[13], (2006). International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 16

17 Code development for tritium behaviour Numerical analysis code, THYTAN has been developed to estimate tritium behaviour. Tritium generation in the core 6 Li (n, α) 3 H, 7 Li (n, nα) 3 H, 3 He (n, p) 3 H, 10 B (n, 2α) 3 H, 235 U(n, f) 135 Xe, 133 I,, 3 H Removal by HPS (HPS: Helium Purification System) Permeation to downstream Isotope exchange reactions, etc. The THYTAN code will be validated by tritium concentration data measured by the HTTR 950 o C long term operation planned in International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 17

18 Evaluation of Toxic Gas IS process generates and contains toxic gas. (SO2, SO3, HI, etc.) Inflowing toxic gas to reactor control room (C/R) should be avoided. Examples of atmospheric toxic gas concentration Concentration (mg/m3) 1.00E E E E E E+00 SO2 5min 10min 20min 30min 45min 60min Toxic gas diffusion evaluation and risk analysis is underway. Ventilation and air conditioning system, gassensing system, offset distance are under designing. リファレンス追加 Concentration in C/R E-01 Concentration of toxic gas in C/R Distance (m) ,000 Distance (m) 1.00E Distance (m) International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 18 Risk (/yr) 1.00E E E E E E E E-07 Toxic gas risk for neighboring public

19 Prevention of tritium permeation IS process should be exempted from radioactivity release control. Methodology to reduce tritium concentration in the produced hydrogen should be developed. Code for tritium behaviour should be developed for safety case study. International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 19

20 Candidate Layout of HTTR-IS system High pressure apparatus which contains toxic gases is covered by walls, ceiling, & ventilation systems No apparatus between the reactor & HI decomposer. High-Temp. Isolation Valve HTTR HI decomposer H2SO4 decomposer Bunsen reactor 30m Control room for hydrogen production IS process HI distillation column 103m Thermal expansion of the concentric hot-gas-duct is absorbed by hightemp. bellows Partition walls is installed between reactor & apparatus which contains burnable gases. Appropriate distance is kept between reactor & partition walls. International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 20

21 Pre-Conceptual design of the HTTR-IS system Flow diagram of the HTTR-IS system H2 2HI H2 + I2 Combined H 2 SO 4 decomposer O2 H2O H2SO4 SO2 + 1/2O2 + H2O DRAFT Rich Lean 2H2O + SO2 + I 2 H2SO4 + 2HI Mixer-settler type Bunsen reactor Hydrogen production rate : Approximately 1000Nm 3 /h International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 21

22 Pre-Conceptual design of the HTTR-IS system Proposal of Combined H 2 SO 4 decomposer* Combining 3 components (H 2 SO 4 evaporator, SO 3 decomposer, regenerative heat exchanger ) Component & Piping number reduction Connection number reduction Prevention the H 2 SO 4 solution outflow to the downstream during the abnormal events Dual-pipe SO 3 SO 2 + ½O 2 Upper heat exchange part He C H 2 SO 4 SO 3 + H 2 O H 2 SO C Lower heat exchange part He C He C Combined type H 2 SO 4 decomposer (conceptual design) * Patent No International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 22

23 Pre-Conceptual design of the HTTR-IS system Proposal of Mixer-settler Type Bunsen Reactor* Combining 3 components (Bunsen reactor, Liquid-liquid separator, liquid transfer pump ) Component & piping reduction Connection reduction Mixing & separation enhancement Vessel overheating prevention I2 H2SO3 H2O SO2 H2SO3+H2O SO2 H2SO4+HI Bubbled SO2 gas H2O (Jet nozzle) H2SO3+H2O Mixer I2 H2SO4 Mixer-settler type Bunzen reactor (conceptual design) H2SO4 + HI Lower mixer Upper mixer * Patent No International Conference on Non-Electric Applications of Nuclear Power, April 2007, Oarai, Japan 23